Thanks to Vaughn for suggesting this week's episode topic about Venus the cat and her unusual coat pattern!

Further reading:

Mystery Cats of the World Revisited by Dr. Karl P.N. Shuker

Further listening:

Half-siders and sea monkeys Patreon episode from December 2018 (unlocked episode)

Venus the cat:



"Half-sider" birds can be spectacular:



Half-side chimeras are not just restricted to birds:



Ranger the "black lion" (photo by Peter Adamson, from this site which you should also read). Note the black patch on his right front leg:



Show transcript:
Welcome to Strange Animals Podcast. I’m your host, Kate Shaw.
This week I had planned to release our updates episode, but I didn’t have time to finish it. The 2022 updates episode will run in September instead, since we’re doing Invertebrate August again this year!
Way back at least a year ago and possibly more, Vaughn suggested we do an episode about “rare two-tone animals like Venus the cat.” I put the suggestion on my list and totally forgot about it until today, when I saw it and thought, “hmm, who’s Venus the cat?”
If you don’t already know, Venus is a beautiful cat whose coloration is mostly what’s called tortoiseshell, meaning she has a mixture of colors on her body, in her case black and orange. But Venus’s face is completely black on one side with a green eye, but orange tabby on the other side with a blue eye. She also has a white bib and white on her paws.
Venus became famous after the family who adopted her as a stray in 2009 posted pictures of her online. Her coloration is so unusual that everyone wondered what caused it. The answer is that we aren’t exactly sure, but veterinarians and experts in cat genetics do have some pretty good ideas.
There are probably several things going on genetically with Venus that resulted in her interesting coloration. Her different-colored eyes are one result. When an animal has different-colored eyes, called heterochromia iridis, there are a number of possible causes, from an injury to one eye to various genetic conditions. Sometimes it’s not complete, meaning one eye may be partly a different color. It even happens in people sometimes, although it’s rare.
In Venus’s case, researchers think her heterochromia may be due to a gene that produces what’s called piebaldism. A piebald animal has white markings when an ordinary animal of the same species doesn’t have any white markings. Some animals who naturally have a white pattern may have the word pie or pied or just bald hidden in their name, such as the magpie and the bald eagle, because it used to mean just an outfit with different contrasting colors. In the story of the pied piper, the piper had on a suit made of different colors.
The white patches of a piebald animal actually don’t have any pigment, and if a white patch is over an eye, the eye may also lack pigment and appear blue. That’s pretty common in piebald or pinto horses or in some dog breeds with white markings. The piebald gene may also affect one or both eyes even if a white patch doesn’t cover the eye, which some researchers think may be the case in Venus. Her left eye is blue even though the left side of her face is orange tabby.
Venus’s unusual facial fur coloration may be due to a condition called chimerism. Chimerism happens long before an animal is born—in fact, it happens within a few hours after an egg cell is fertilized. I’ll do my best to explain it. A lot of the next section comes from a Patreon episode from 2018, and if you want to listen to the original I’ve unlocked it for anyone to listen to and put a link in the show notes.
As soon as an egg cell is fertilized, it starts to divide into more cells, which divide into more cells, which divide into more cells, and on and on. After a while, the groups of cells start to differentiate into parts of the body. Some cells become a heart, others become toes, and so on. Eventually there’s a whole finished baby ready to be...